How do I complete a punnett square with 4 traits?

There are not 4 traits in this example- only two: Smooth/wrinkled and green/yellow. To cross them, you would have to know the genotype of the smooth, green pea: SSGG or SsGg? The wrinkled, yellow pea is automatically ssgg. The SSGG pea produces one type of gamete, SG, so the PUnnett square is just a 1x1. The SsGg pea produces 4 gametes, SG, Sg, sG, and sg, so the Punnett square is a 1x4...